Bittorrent basically runs on social norms, and people's willingness to help their community. Or people go to private trackers, where contributing is a requirement for being in the community and having access to its resources.

Blockchains are built under the assumption that everyone is selfish and untrustworthy. Which is a decent assumption when building a crypto currency, but that doesn't mean that every system has to run like that.

A token system can incentivize cooperation in a hostile environment with selfish nodes. But in a friendly environment you might not need the same level of incentives.

I see some similarity here to the world of private torrent trackers. You want a Linux ISO, I want a Linux ISO, we're all working towards the same goal. So we're already incentivized to cooperate, without getting money involved. And trackers also have things like minimum seeding ratios to keep people honest. In the case of AI, you and I both want to generate images, so we're also working towards the same goal, so let's help each other out so both of our workloads finish faster. Maybe idealistic, but I think it could work.

In the heyday of BitTorrent sharing was the incentive, and still is I imagine. We don't need to financialize everything.

That's more cryptocurrency than blockchain.

Blockchain as such has nothing to do with the costs of a node and incentives to run one

That's a different question. But BitTorrent does fine with simple tit-for-tat rules, no tranferable tokens required.